Cannot see how measures are calculated, blank Power Query

I have downloaded a pbix file from the online platform, the file was created by someone else. In the file, there are connections to mongo db, big query and a third party database, the first two I have access to, the third I do not.

I want to see how they calculated some measures, as this is a large file, however I cannot see the usual top bar with a formula. 

I can see only report view and model view, not the third one usually visible (screenshot below) .

When Igo to Transform data, I get the warning as in screenshot below. I add a local model, it seems to be processing and finish, and then I get the Transform data with absolutely nothing like in screenshot below

I never worked with a report uploaded by someone else outside the organisation and I dont know how to solve this so i can document how these measures are calculated, and edit if necessary.

Does anyone have an idea what I can do in this case?